This invention relates to plastic screw caps for use with small hand held containers, such as are provided to hold and dispense cosmetic products. More particularly, the invention relates to such caps wherein a plurality of seals is provided to insure the preservation of the cosmetic product during shipping and storage, extended shelf life, etc.
In the past various types of plastic screw caps having multiple seals have been proposed and produced. Some of these prior screw caps have involved deformable depending skirts of flanges, whereas others have involved plug formations insertable in the neck of the cooperable container. The prior caps have in most cases not only involved complicated mold forms which were expensive, but also required the use of a substantial amount of plastic material in order to effect the desired double sealing function. Thus, there was entailed a considerable mold cost and in addition the unit cost per cap was not inconsequential, particularly since the cost of the plastic molding material has now become a factor due to increasing petroleum costs.
Moreover, in many instances the configuration of the cap did not insure the preservation of the seals if the plastic material thereof deformed by reason of shrinkage, or adverse environmental factors.